Understanding measurement, monitoring and verification (MM&V) needs in the environmental context of potential subsea carbon dioxide (CO₂) storage projects (Carbon Capture and Storage [CCS]) is a challenging task globally. Unmanned surface vehicles (USV) equipped with acoustic sensors are an attractive option for detecting gas leaks due to their spatial and temporal coverage potential. Here, a SIMRAD Wide Band Transceiver Mini acoustic sensor is evaluated for detecting CO₂ leaks in shallow coastal water (<20 m depth). Small flows of CO₂ (0.34–3.90 tonnes CO₂ gas yr⁻¹) were released into the water column. The plumes were detected with the acoustic system with the results highlighting their dynamic nature. A survey simulation model showed that the probability of detecting a leak inside a 5 × 10 km survey area improved depending on the number of leaks within it, with 100 % detection probability for two leaks (>7.8 tonnes CO₂ gas yr⁻¹) achieved with a survey time of 600 h. As the number of leaks increased to 40 (> 156 tonnes CO₂ gas yr⁻¹) the survey duration reduced to ∼110 h for 100 % probability of detecting a plume.

These detection flow rates are well below the upper limits proposed by IPCC (2005) for climate mitigation for a release of 1% in 1000 years for most proposed CO₂ storage sites. Regulatory requirements for CCS sites are still evolving to address societal expectations and environmental monitoring needs. This work assists in determining detectable leak rate thresholds that can be detected in the marine environment using acoustic sensors.

在潜在的海底二氧化碳（CO ₂）储存项目（碳捕集与封存[CCS]）的环境中，了解测量，监视和验证（MM＆V）的需求是全球一项艰巨的任务。配备声传感器的无人水面车辆（USV）由于其时空覆盖潜力而成为检测气体泄漏的诱人选择。在此，对SIMRAD宽带收发器迷你型声学传感器进行了评估，以检测浅海（<20 m深度）中的CO ₂泄漏。小流量的CO ₂（0.34–3.90吨CO ₂气体yr ^-1）释放到水柱中。通过声学系统检测出羽流，结果突出了它们的动态特性。一个调查模拟模型表明，根据5×10 km调查区域内的泄漏数量，发现泄漏的可能性有所提高，两次泄漏（> 7.8吨CO ₂气体yr ^-1）的检测概率为100％调查时间为600小时。随着泄漏次数增加到40次（> 156吨CO ₂气体yr ^-1），调查持续时间减少到约110小时，有100％的可能性检测到烟羽。

这些检测流速远低于IPCC（2005）提出的气候缓解上限，大多数拟议的CO ₂储存地点在1000年内释放了1％。CCS站点的监管要求仍在不断发展，以满足社会期望和环境监控需求。这项工作有助于确定可以使用声学传感器在海洋环境中检测到的可检测泄漏率阈值。